The focus of the laboratory research is an investigation of the regulation of expression of the metallothionein locus, CUP 1, in the yeast Saccharomyces cerevisiae. Metallothioneins are small cysteine rich proteins found in most eukaryotes, which bind to heavy metals, and thus protect the cell from toxification. Expression of the CUP 1 gene in yeast is increased in the presence of metal ions such as copper or silver. This induction is mediated through upstream elements located in the promoter region of Cup1, which serve as binding sites for the transacting factor, ACE1. In the absence of metal ions, ACE1 exists as a free protein, and expression of CUP1 is very low. In the presence of copper ions, ACE1 binds to the CUP 1 promoter and induces expression. The ACE1 gene was identified and cloned in this laboratory.